1. Field of the Invention
This invention relates to a torque sensing type disc brake arranged to permit measurements of a braking torque which represents the output state of a braking device.
2. Description of the Prior Art
A disc brake is arranged, as well known, to brake the rotation of a rotor by causing a pair of friction pads to frictionally engage the revolving faces of the rotor with an input obtained from hydraulic or mechanical input means. Meanwhile, it has been variously arranged to have a braking torque which is applied to the friction pads received by some fixed member of a vehicle (such as a knuckle, a support member or the like) either directly or through a caliper or the like. The details of the disc brakes of this kind have been known, for example, from the specifications of British Patents No. 1500907, No. 1095368, etc.
Further, for ensuring safe brake application to vehicles, the braking devices have been arranged in functional combination, for example, with a proportioning valve for controlling the allocation of braking forces to front and rear wheels in connection with a shift which takes place in the load position during brake application; a booster which boosts the pedalling force of a brake pedal, an antilock device for preventing wheels from falling into a locked state on a frozen road surface or the like, and so on.
With each of four wheels of a vehicle assumed to be equipped with a braking device of the above-stated kind, it is preferable for a safe braking operation on a vehicle to have a feedback control system arranged to detect the output states of these braking devices and to feed back the input control device of each of these braking devices with information on the output state detected. Such feedback arrangement is advantageous for adequate control, for obtaining always a constant braking force in response to a given pedalling force on the brake pedal and for antilock control over the wheels. In actuality, however, there has been known no control system that is capable of directly detecting the output of a braking device, although there has been some known arrangement to detect the rotating state of a wheel, for example, in such a manner as disclosed in the specification of U.S. Pat. No. 3,626,226. The reason for the absence of the above-stated control system resides mainly in the difficulty of measuring and detecting the output of a braking device in the form of a physical quantity with a sufficiently high degree of reproducibility.